1. Field of the Invention
The present invention relates to a liquid delivery apparatus, and particularly to a liquid delivery apparatus actuated by a piezoelectric element.
2. Discussion of Related Art
For instance, there is conventionally known an ejecting apparatus where a plurality of pressure chambers each accommodating a liquid is closed by a diaphragm which is deflected by a piezoelectric element so as to eject a droplet of the liquid from a nozzle. In such an apparatus, since the pressure applied to the liquid accommodated in the pressure chamber is increased with an increase in the amount of deflection of the diaphragm, the diaphragm is desired to be easily deformable or displaceable.
A technique to increase the deflection of the diaphragm is disclosed in JP-A-9-104109 for instance, which teaches an ink jet head in which a piezoelectric element of unimorph type is disposed on a plurality of segments extending inward from a peripheral part of a pressure chamber having a circular shape when seen in a direction perpendicular to the plane of the diaphragm while not actuated. The central part of the diaphragm partially defining the pressure chamber is pressed by the piezoelectric element to eject a liquid droplet. According to this technique, the amount of expansion or displacement of the diaphragm can be increased. However, the structure of this ink jet head is complicated. In addition, when the piezoelectric element is actuated, both of the segments disposed on a lower surface of the piezoelectric element and the diaphragm disposed on an upper surface of the piezoelectric element, need to be deformed in accordance with the displacement of the piezoelectric element. This leads to inefficiency in the displacement of the diaphragm.